Dull bit indicator



I July 31, 1951 M. EJTRUE DULL BIT INDICATOR Filed Dec. 22, 1948INVENTOR- MML ATTORNEY.

Patented July 31, 1 951 2,562,833 DULL BIT INDICATOR Martin Houston,Tex., assignor, by mesne assignments, to ,Standard Oil Development ompny, Delaware Elizabeth, N. J., a corporation of Application December 22,1948, Serial No. 66,662

' 3 Claims. (01. 255- 1) This invention relates to a drill bit used fordrilling 'boreholesinto subsurface formations. More particularly, thisinvention relates to a drill bit which, when it is worn by apre-determined amount during drilling operations, will give a signal ofsuch wear at the surface of the earth. Y

In the drilling of boreholes into subsurface formations by the rotarydrilling method, particularly in drilling boreholes for the productionof minerals, such as oil and gas, the drill bit attached to the end ofthe drill stem is subjected to conditions which cause rapid wear of thecut ting edges of the bit blades. The blades of several bits areordinarilyworn off in drilling such a well. Of course, when thebladesare worn off a in the mud stream used with the drill string andparticular bit, the drilling crew must pull the for determining thepoint when the cutting blades of the drill bit are worn to such anextent as to require replacement of the bit; consequently, the selectionof the time when the drill bit should be removed from the hole is whollywithin the judgment of the drilling crew. As would be expected,conventional drill bits are sometimes removed from the hole before theblades have been worn to the point where the drill bit should really bereplaced. On the other hand, and perhaps more commonly, the drill stemis some-. times not withdrawn from the hole and the bit replaced untillong after the blades have been worn to such an extent that little or nohole is being made. As a matter of fact, drilling is sometimes continueduntil the bit blades. have been completely worn. off the bitv body andthe bit body itself damaged by wear.

Although excessive wear of the cutting ,edge ofthe bit blades is the.most, frequent reason for replacement of conventional drill bits, .11;

sometimes happens. that the bit, should be. re,-.

placed because it has become worn out of gauge. Here again the drillingcrew has no positive means of knowing when the bit has become so worn. Adrill bit is said to'be worn out of gauge when the reaming edges of thebit blades have been worn to such an extent that the-diameter of thehole being made is smaller than may conveniently be tolerated. Forexample, the diameter of a hole drilled with a 'bit having wern reamingedges may not bev sufllciently greatto permitv the free passage of a newunworn drill bit subsequently introduced into the hole? When thiscondition exists, the borehole walls, rriustbe enlarged by reaming in asuitable-manner as with a new-bit. Not only does reaming consum'etiinebut it also entails the.risk; of ,a stuck drill bit.

It is an object of this invention to provide a drill bit which, whenworn by'a re-determined amount, will cause an increase in 'fiuid''pressure thus give a signal to the drilling crew indicating that thedrill bit should be removed because of excessive wear.

, It is a further object to provide a drill bit,

4 the body of which will not be damaged during drilling operations andin which the construction is such that repair of the used bit isconvenient and simple.

The foregoing objects, as well as other advantages, are attained by thepresent invention as will be apparent from the following detaileddescription taken in connection with the accompanying drawing in whichFig. l is a side view, partly in cross section, of a drill bitconstructed in accordance with the present invention; and

Fig. 2 is a front View of the embodiment shown in Fig. 1.

' Referring to the drawing, in which'like numerals refer to likeelements throughout, the drill bit of my invention consists of a body l6and cutter blades II and [2. The body I!) may be affixed to the lowerend of a drill stem l3 by any suitable means, such as by threads, thesaid drill stem being of the conventional design fluidly connectiblewith a source of drilling fluid under pressure. Body I0 is provided witha hollow internal portion M in fluid communication with drill stem I3when drill stem I3 is connected with body l0. Ducts l5, conventionallytermed eyes or water courses, fluidly connect the hollow internalportion Id of body Ill With the outer surface'of said body, the outerterminus of ducts 15 being above the upper edge of bit blades H and I2and normally directed in front of the cutting edge of said blades. Bitblades II and I 2 may be of any desired design and are preferably madeof hard, tough, metallic materials. The reaming edges It and I! of bitblades H A and I 2, respectively, are approximately parallel to eachother and to the longitudinal axis of body 150;. Cutting edges l8 and IQof bit blades II and [2, respectively, are normally slightly beveled.outwardly and downwardly as shown. The, cutting face 20 of bit blade llis disposed approxi- 22- is smaller in diameter at the portionthereofadjacent the hollow internal portion 14 thani the remainderthereon-thus defining outwardly tight seal between plug 24 and the wallsof duct Rod anchor 28 is aifixed to the outer surface of bit body Inabove duct 22 in any suitable manner, as for example by welding, rodanchor 28 being traversed by vertically extending duct 29. Plug 24 isheld firmly in place in duct 22 against seat 23 by means of rod 30 whichis adapted to have its upper end inserted in duct 29 carried by rodanchor 28 and its lower end tack-welded to blade preferably on the backside of said blade, as shown. Rod 30 extends downwardly along blade IIto a point atvleast below the lower edge of body and it may extend toany point below such lower edge as desired. In operation, rod 30 willprevent plug 24 from being pushed outwardly out of duct 22 by thepressure exerted by the drilling fluid circulated through water courses[5. Rod 30 will retain plug 24 in the aforementioned position until suchtime as bit blades II and I2 have been worn to the point at which rod 39has been tack-welded toblade II, at which point the lower end of rod 30is also worn away. When the weld at the lower end of rod 30 is wornaway, rod 3|] will drop out of duct 29 of rod anchor 28, thus permittingplug 24 to be forced out of duct 22 by reason of the pressure exerted bythe drilling fluid. After plug 24 has been forced from duct 22, drillingfluid will, of course, flow through duct 22, thus causing a sharp dropin the pressure exerted by the drilling fluid and providing a signal tothe drilling crew that the drill bit has been worn to a point wherereplacement is required.

By tacking rod 39 in close proximity to a reaming edge of the bit, asfor example by placing it in close proximity to reaming edge 16 of bladeII, the wearing of bit blade ll out of gauge may also be indicatedprovided such wear occurs before the cutting edge l3 of bit blade I Ihas been worn to the point to which rod 30 extends vertically.

It will be understood that various modifications may be made withoutdeparting from the spirit of the present invention or the scope of theannexed claims.

What I wish to claim as new and useful and desire to secure by LettersPatent is:

1. A drill bit comprising, in combination, a body having an internalchamber and means for mechanically affixing said body to a drill stemhaving a hollow passageway therethrough, said body defining a fluidpassageway interconnecting said internal chamber with the hollowpassageway of said drill stem, a bit blade having a leading and atrailing face and having a cutting edge on its lower end and a sideedge, said blade being affi'xed to the lower edge of said body, saidbody having at least one first duct fluidly connecting said internalchamber with the external surface of said body above the cutting edge ofsaid bit blade and directed ahead of the leadin face thereof, said bodyhaving at least one second duct located in the side wall of said bodyfluidly connecting said internal chamber with the exterior surface ofsaid body, a plug releasably disposed within and normally closing said 4end aflixed to said cutter blade below. the lower end of said'body'andmaintaining said plug within said second duct normally closing saidsecond duct, said rod member being adapted to be removed from said bodyand said cutter blade by cutter blade wear.

2. A drill bit comprising, in combination, a body having an internalchamber and means for mechanically aifixing said body to a drill stemhaving a hollow passageway therethrough, said body defining ,a fluidpassageway interconnecting said internal chamber with the hollowpassageway of said drill stem, a bit blade having a leading and atrailing face and having a cutting edge on its lower end and a sideedge, said blade being affixed to the loweredge of said body, said bodyhaving at least one first duct fluidly con-, necting said internalchamber with the external surface of said body above the cutting edge ofsaid bit blade and directed ahead of the leading face thereof, said bodyhaving a second duct located in the side wall of said body fluidlyconnecting said internal chamber with the exterior surface of said body,a, closure means disposed within and normally closing said second ductto the passage of fluid therethrough, a rod member aflixed to said bodywith its lower end affixed to said cutter blade below the lower end ofsaid body and maintaining said closure means within said second ductnormally closing said second duct, said rOd member being adapted to beremoved from said body and said cutter blade by cutter blade wear.

3. A drill bit comprising a hollow body having a releasable connectionat its upper end for connection to a hollow drill stem and provided withcutter blades at its lower end, each blade having a cutting face, afirst duct for each blade fluidly connecting the lower end of theinterior. hollow portion of saidv body with the exterior of said bodyahead of the cutting face of each of said blades, said body having atleast one second duct located above said first ducts and fluidlyconnecting the interior of said body with the exterior of said bodyabove said first ducts and one of said cutter blades, a closure memberreleasably disposed within and normally closing said second duct to thepassage of fluid therethrough, a bar member'afiixed at its upper end tothe outer sur-- face of said body and extending across said closuremember, and aflixed at its lower end to a cutter blade below said firstand second ducts to maintain said closure member within said secondduct, said bar member being released upon 55 MARTIN E. TRUE.

' REFERENCE S CITED The following references are of record in the fileof this patent:

UNITED STATES PATENTS Number Name Date 2,226,655 Beaven Dec. 31, 19402,296,183 Richard Sept. 15, 1942 2,457,960 Walker Jan. 4, 1949'2,461,164 Lewis Feb. 8, 1949 2,468,905 Warren May 3, 1949 2489,63?Thriftet al. Nov. 29, 1949 I FOREIGN PATENTS Number Country v 7 Date a 088 German a g p ,8 9.08.

